As an image forming apparatus such as a printer, a facsimile, a copier, a plotter, a multifunctional apparatus integrating them, or the like, for example, an inkjet recording apparatus is well known as a liquid discharge recording scheme by using a recording head which is formed by a liquid discharge head (droplet discharge head) for discharging ink droplets. In the image forming apparatus of the liquid discharge recording scheme, an image is formed by discharging ink droplets from a recording head onto a sheet being conveyed. The sheet is not limited to a paper sheet. The sheet may be an OHP (Over Head Projector) and other types of sheets onto which the ink droplet or other liquid can be adhered, and may be called as a medium to be recorded, a recording paper, a recording sheet, or the like. Recording, printing, and the like are synonymous with forming an image. There are a plurality of serial type image forming apparatus for forming an image by discharging droplets while the recording head moves in a main scan direction, and a line type image forming apparatus using a line type head for forming an image by discharging droplets in a state in which the recording head does not move.
In order to detect a main scan location of a carriage mounting the recording head, the serial type image forming apparatus includes a linear encoder formed by an encoder scale arranged in the main scan direction and an encoder sensor mounted at a carriage side. However, since the image is formed by discharging droplets from the recording head, when mist is adhered to the encoder scale, misreading of a head location occurs and detection accuracy of a carriage location is degraded. Thus, image quality is degraded.
Accordingly, Japanese Laid-open Patent Application No. 2005-081691 discloses that the linear encoder is formed by the encoder scale arranged in a vicinity of a carriage conveyance belt and an encoder sensor provided at a lateral surface of the carriage, and a shielding plate is arranged between an upper portion of the carriage conveyance belt at least and the encoder scale.
Moreover, Japanese Laid-open Patent Application No. 2001-113772 discloses that the linear encoder is formed by the encoder scale arranged in the vicinity of the carriage conveyance belt and the encoder sensor provided at the lateral surface of the carriage. A cover is provided to cover the encoder sensor and a part of the encoder scale in the vicinity of the encoder sensor. The cover includes a guide part for guiding the encoder scale to a predetermined location with respect to the encoder sensor.
However, in the above described technologies, since the recording head of the carriage and the encoder scale are arranged within the same space, the mist, which is discharged with the droplets from the recording head, goes around the shielding plate and reaches and adheres to the encoder scale or to a portion which is not shielded by the cover.